1. Field of the Invention
The present invention relates to an underwater weighing container and an underwater weighing container unit for receiving a weight of a solid specimen immersed in a reference liquid and a buoyant force exerted thereon. The present invention also relates to an apparatus for measuring a specific gravity of the solid specimen.
2. Description of the Related Art
Generally, the commonly employed method for determining a specific gravity of a solid specimen without knowledge of its volume is to weigh the solid specimen in air, measure a weight of the solid specimen immersed in a reference liquid or a buoyant force exerted thereon, and use the obtained values for calculating the relevant specific gravity based on the following equation (1):Specific Gravity=Weight in Air/(Weight in Air−Weight in Liquid)=Weight in Air/Buoyant Force  Equation (1)
As will be exemplified hereinafter, methods of weighing a solid specimen both in air and in a reference liquid, or measuring a weight of the solid specimen in air and a buoyant force produced by the solid specimen, for calculation of the relevant specific gravity have been applied to a number of conventional apparatus for measuring specific gravity. One such example is a specific gravity measuring apparatus 5A in FIG. 8, wherein a solid specimen 2 is first hung and suspended in air and then placed inside a liquid bath 3 to measure its weight by means of an electronic weighing scale 7, for determining the specific gravity. As shown in FIG. 9, another conventional specific gravity measuring apparatus 5B has an underwater weighing container 1A arranged on an electronic weighing scale 7, allowing the underwater weighing container 1A to mount a solid specimen 2 thereon in a liquid bath 3B. With this configuration, after the underwater weighing container 1A holding the solid specimen 2 is subjected to measurement, the corresponding tare weight is subtracted from the obtained weight to determine specific gravity of the solid specimen 2. The patent literatures pertaining to these apparatuses for measuring specific gravity are Unexamined Japanese Patent Application Publication Nos. H11-230885 and 2002-243615.
The aforementioned configurations are employed in the conventional specific gravity measuring apparatus and the underwater weighing containers. However, the method of hanging and suspending the solid specimen 2 as shown in FIG. 8 is troublesome, due to the need to replace and suspend the solid specimen 2 having different shapes. In the method of providing the underwater weighing container 1A for measuring the weight of the solid specimen 2, as shown in FIG. 9, the solid specimen 2, if its specific gravity is lower than that of a reference liquid, will be floating. As representative measures to prevent the solid specimen 2 from floating, a sinker frame 8 as shown in FIG. 9, or a lid (not illustrated) may be placed in a reference liquid L. If any such measure is to be implemented, users will be required to insert and remove the sinker frame 8 or to open and close the lid, whenever conducting weight measurement. This method, as illustrated in FIG. 8, is inconvenient for users. Depending on whether the solid specimen 2 sinks or floats in the reference liquid L, users will be required to employ a different configuration of the underwater weighing container 1A. This can increase users' work load for maintenance and management of the apparatus for measuring specific gravity. The amount of the reference liquid L used for the measurement process also increases.